Microphones (e.g., MEMS capacitor mics) are known in the art and typically convert sound pressure to electrical signals. The corresponding conversion factor is often referred to as the microphone's sensitivity. That sensitivity typically varies with frequency. In many cases microphones have a relatively flat response at audio frequencies while exhibiting a significant peak in the ultrasonic region due to mechanical resonances of the sensor. Although such peaks occur in the inaudible ultrasonic region, such peaks can nevertheless result in audible distortion.
In some application settings it can be desirable to increase a microphone's sensitivity. Unfortunately, typical approaches for boosting sensitivity in the audio band also boost sensitivity in the ultrasonic band. As a result, boosting sensitivity can result in increased unwanted audible distortion due to boosted peaks in the ultrasonic band.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present teachings. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present teachings. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.